Disabling the change cache by default.

Since the change cache can mess-up multi-server setups,
it is now disabled by default.

Change-Id: Ia8dc83f675bbfc1f6467cfed29a964554e2b1951

gerrit-server/src/main/java/com/google/gerrit/server/git/ChangeCache.java

@@ -48,7 +48,7 @@ public class ChangeCache implements GitReferenceUpdatedListener {
         cache(ID_CACHE,
             Project.NameKey.class,
             new TypeLiteral<List<Change>>() {})
-          .maximumWeight(1024)
+          .maximumWeight(0)
           .loader(Loader.class);
       }
     };